An electrophotographic image processing apparatus to deal with image data and other data, such as a digital multi-function machine (MFP=Multi-Function Peripherals) is known. The image processing apparatus uses a parallel system bus, such as a PCI bus (Peripheral Components Interconnection bus), as an interface between a plurality of devices, such as a scanner and a printer. Furthermore, the image processing apparatus has an ASIC (Application Specific Integrated Circuit) for each function. For example, the image processing apparatus has an ASIC to process image data from a scanner. For example, the image processing apparatus has an ASIC to perform expansion processing of print data from a PC (Personal computer). For example, the image processing apparatus has an ASIC and so on to process image data to a printer. Each of these ASICs connects to a local memory.
The above-described image processing apparatus constantly manages a large amount of data which are transferred between respective devices, such as a scanner and a printer. The image processing apparatus manages a large amount of data, and in addition, it is necessary for the image processing apparatus to control the respective devices so that a scanner and a printer and so on can achieve a function as an image input/output device. However, there is a case where a high speed processing is required in the image processing apparatus. Specifically, there is a case where speeding up of a CPU and a main memory is required. Furthermore, there is a case where support for an application which needs a large amount of calculation is required. Furthermore, there is a case where improvement and so on in the connectability with an external device is required. In these cases, it is necessary that the image processing apparatus also speeds up a speed (transfer band) of a flow of various data such as image data and a control command.
Furthermore, an image processing apparatus using a high-speed serial bus such as a PCI express is known. This image processing apparatus uses a high-speed serial bus, to broaden the data transfer band. The image processing apparatus broadens the data transfer band, and thereby intensively process the data which has been processed using a local memory, using a main memory. As a result, since a plurality of memory devices are eliminated in the image processing apparatus, cost reduction can be achieved.
On the other hand, in the image processing apparatus using a high-speed serial bus, since data is intensively processed using a main memory, there is also a demerit that difficulty increases regarding the arbitration of data transfer. In the image processing apparatus, particularly in the MFP, there is a case where a CPU starts operations (reading/printing of a document) of a scanner and a printer, while processing various applications in the background. In such a case, since a sheet is conveyed in the MFP at a constant speed, it is necessary to perform data processing so as to meet the conveyance of a sheet.
It is necessary that in a scanner image processing pass, the image processing apparatus writes image data outputted from a scanner in a main memory without delay. Furthermore, it is necessary that in a printer image processing pass, the image processing apparatus reads print image data expanded on a main memory without delay and outputs the data to a printer.